Thin polished plates such as silicon wafers and the like are a very important part of modern technology. A wafer, for instance, may refer to a thin slice of semiconductor material used in the fabrication of integrated circuits and other devices. Other examples of thin polished plates may include magnetic disc substrates, gauge blocks and the like. While the technique described here refers mainly to wafers, it is to be understood that the technique also is applicable to other types of polished plates as well. The term wafer and the term thin polished plate may be used interchangeably in the present disclosure.
Semiconductor materials may be inspected for defects such as, e.g., surface imperfections, particles, irregularities the thickness of thin film coatings, and the like, which may hamper the performance of the semiconductor material. Some existing inspection systems direct a beam of radiation on the surface of the semiconductor material, then collect and analyze light reflected and/or scattered from the surface to quantify characteristics of the surface.
More specifically, existing systems generally utilize a beam scanner created by having a laser source focused on a crystal. The crystal is shifted to a fresh area when the currently exposed area has degraded to an undesirable level (i.e., end of life). While shifting from a discrete crystal site at the end of its life is appropriate for the defined limits on lifetime of a laser sub-system, however, from a system perspective, shifting from an exposed area that has degraded to its end of life to a fresh area requires re-calibration or re-alignment, which is very time consuming.
Therein lies a need for providing a laser source for inspection systems without the aforementioned shortcomings.